1. Field of the Invention
The present invention relates to an LSI package provided with an interface (I/F) module, an interposer and an I/F module which are used in the LSI package, and a transmission line header implementing the I/F module.
2. Description of the Related Art
With improvements in the performance of electrically interconnected devices such as bipolar transistors and field-effect transistors, remarkable developments in the operation speed is being attempted in large scale integrated circuits for signal processing (hereinafter described “signal processing LSI”). However, the operation speed on a printed circuit board level mounting the signal processing LSI is still lower than the operation speed inside the signal processing LSI, although the inside operation speed of the signal processing LSI is inherently high, and further, on a rack level packaging hierarchy implemented by the printed circuit boards, the operation speed becomes further lower. The above-mentioned operation speed problems are caused by increases in transmission loss, noise, and electromagnetic interference associated with the electrical interconnections, which increase as the operation frequency becomes higher. Namely, it is inevitable that as the wiring length becomes long, the operating frequency becomes lower so as to ensure the signal quality. Therefore, such a tendency that the packaging technology limits the operation speed of the system rather than the operation speed of the signal processing LSI, has become more and more significant recently in the electrically interconnected device.
Taking such problems in electrically interconnected devices into consideration, optically interconnected devices configured to establish communications between signal processing LSIs by optical interconnection are proposed. In the optical interconnection, since the frequency dependence on losses, the electromagnetic interference in the distribution lines and noise associated with ground potential fluctuation can be ignored in a frequency range from direct current to a high frequency band over 100 GHz, communication of Gbps can be easily realized. Such an optically interconnected device establishing communications between signal processing LSIs by optical interconnection is disclosed, for instance, in NIKKEI ELECTRONICS, No. 810, pp 121-122, Dec. 3, 2001, in which a structure directly mounting an I/F module, which is adapted for external connection of high-speed signals, on an interposer which has a signal processing LSI, is proposed.
In the above-mentioned earlier technology, it is difficult to carry out board mounting of an interposer in an actual interposer mounting process, since the board mounting of an interposer is carried out under the condition where an interposer is mingled with an I/F module.
For instance, since the I/F module has an optical transmission line such as an optical fiber, etc, it is not possible to give heat treatment by putting the optical fiber into a solder reflow furnace of the interposer as it is. The problem is not limited to a case in which the optical transmission line is employed, since the same problem arises when an electrical transmission line such as a small coaxial cable is used for the transmission line.
Then, such methodology in which the optical transmission line is formed so that it can be detached from the I/F module by a detachable optical connector may be considered as disclosed in NIKKEI ELECTRONICS. However, in the detachable optical connector methodology, protectors for protecting optical semiconductor elements and optical connectors from mechanical damage and pollution are required. And, in addition, various architectures for lowering the process temperature so as to prevent thermal deformation of joints of the optical connector and for shortening the processing time are required. Because of these requirements, there was a problem being that the mounting condition of other parts which are supposed to be mounted on the same board do not meet with the mounting condition of the I/F module and that existing board assembly equipment was not able to be applied to as they were. Furthermore, the configuration becomes more and more complicated because pressure mechanism and holding mechanism of the optical connector must be provided in the detachable optical connector methodology, and therefore, the manufacturing cost drastically increases.